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Proceedings Paper

Studies of viral DNA packaging motors with optical tweezers: a comparison of motor function in bacteriophages phi29, lambda, and T4
Author(s): Douglas E. Smith; Derek N. Fuller; Dorian M. Raymer; Peter Rickgauer; Shelley Grimes; Paul J. Jardine; Dwight L. Anderson; Carlos E. Catalano; Vishal Kottadiel; Venigalla B. Rao
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Paper Abstract

A key step in the assembly of many viruses is the packaging of double-stranded DNA into a viral procapsid (an empty protein shell) by the action of an ATP-powered portal motor complex. We have developed methods to measure the packaging of single DNA molecules into single viral proheads in real time using optical tweezers. We can measure DNA binding and initiation of translocation, the DNA translocation dynamics, and the filling of the capsid against resisting forces. In addition to studying bacteriophage φ29, we have recently extended these methods to study the E. coli bacteriophages λ and T4, two important model systems in molecular biology. The three systems have different capsid sizes/shapes, genome lengths, and biochemical and structural differences in their packaging motors. Here, we compare and contrast these three systems. We find that all three motors translocate DNA processively and generate very large forces, each exceeding 50 piconewtons, ~20x higher force than generated by the skeletal muscle myosin 2 motor. This high force generation is required to overcome the forces resisting the confinement of the stiff, highly charged DNA at high density within the viral capsids. However, there are also striking differences between the three motors: they exhibit different DNA translocation rates, degrees of static and dynamic disorder, responses to load, and pausing and slipping dynamics.

Paper Details

Date Published: 10 September 2007
PDF: 8 pages
Proc. SPIE 6644, Optical Trapping and Optical Micromanipulation IV, 664404 (10 September 2007); doi: 10.1117/12.739629
Show Author Affiliations
Douglas E. Smith, Univ. of California, San Diego (United States)
Derek N. Fuller, Univ. of California, San Diego (United States)
Dorian M. Raymer, Univ. of California, San Diego (United States)
Peter Rickgauer, Univ. of California, San Diego (United States)
Shelley Grimes, Univ. of Minnesota (United States)
Paul J. Jardine, Univ. of Minnesota (United States)
Dwight L. Anderson, Univ. of Minnesota (United States)
Carlos E. Catalano, Univ. of Washington (United States)
Vishal Kottadiel, Catholic Univ. of America (United States)
Venigalla B. Rao, Catholic Univ. of America (United States)

Published in SPIE Proceedings Vol. 6644:
Optical Trapping and Optical Micromanipulation IV
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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